Pull request template

As discussed in retro, create a tempate for writing better pull requests
so they are easier to review and can be used as documentation in the
future.

.github/pull_request_template.md

@@ -0,0 +1,24 @@
+<!-- Delete sections if not required -->
+
+## Context
+<!-- Why are we making this change? New feature? Bug fix? -->
+
+## Changes proposed in this pull request
+<!-- Describe briefly the technical implementation -->
+<!-- Show any dependencies between pull requests, i.e. this must be merged before or after another -->
+
+## Guidance to review
+<!-- Show how this can be tested or evidence that it is working -->
+
+## Before merging
+<!-- Any extra steps like: delete temp commit, send warning, wait after office hours... -->
+
+## After merging
+<!-- Any extra steps like: update other PR, apply manually, inform someone... -->
+
+## Checklist
+
+- [ ] I have performed a self-review of my code, including formatting and typos
+- [ ] I have [cleaned the commit history](https://www.annashipman.co.uk/jfdi/good-pull-requests.html)
+- [ ] I have added the `Devops` label
+- [ ] I have attached the pull request to the trello card